Vehicles traveling by using electric power supplied from batteries are in wide use. These types of electric powered vehicles include hybrid automobiles traveling by driving forces of an engine and a motor/generator, and electric automobiles traveling by driving force of a motor/generator.
An electric powered vehicle is equipped with a plurality of accessory apparatuses, such as lighting apparatus, air-conditioning apparatus, and audio apparatus. The battery for driving an electric powered vehicle also supplies electric power to the accessory apparatuses. For this reason, an electric power conversion circuit is provided in the electric powered vehicle for dropping the output voltage of the battery and supplying electric power to the various accessory apparatuses in accordance with the voltage after being dropped.
In general, the supply voltage for an accessory apparatus differs in accordance with the function, purpose, and so forth, of the accessory apparatus. To supply electric power to each of a plurality of accessory apparatuses having different supply voltages, equipping the electric powered vehicle with a plurality of electric power conversion circuits having different step-down ratios can also be considered. However, since a plurality of electric power conversion circuits will be required, a problem arises when the circuitry to be installed in the electric powered vehicle increases in scale.
Thereupon, as disclosed in JP 2011-193713 A, there has been proposed an electric power conversion circuit making possible electric power conversion among a plurality of DC ports.
A transformer is used in an electric power conversion circuit installed in an electric powered vehicle to electrically insulate between the battery and accessory apparatus. In this case, a current not contributing to electric power transmission flows to the transformer, and electric power loss may be large depending on the operation of circuitry connected to the primary winding of the transformer and the operation of circuitry connected to the secondary winding of the transformer.
The present disclosure is intended to reduce the electric power loss in the electric power conversion circuit.